This application relates to measurement of processing conditions in target environments, particularly target environments within processing systems used in automated processing of workpieces. Such workpieces may include semiconductor wafers, glass substrates for flat-panel displays and disks for magnetic memories. All patents, patent applications and other documents referred to in this application are hereby incorporated by reference in their entirety for all purposes.
The fabrication of an integrated circuit, display or disc memory generally employs numerous processing steps carried out on a workpiece (production substrate). Each process step may be carefully monitored in order to provide an operational device. Throughout the imaging process, deposition and growth process, etching and masking process, etc., it may be critical, for example, that temperature, gas flow, vacuum, pressure, chemical, gas or plasma composition and exposure distance be carefully controlled during a particular step. Careful attention to the various processing conditions involved in a step may be a requirement of good semiconductor or thin film processes. Any deviation from desired processing conditions may cause the ensuing integrated circuit or device to perform at a substandard level or, worse yet, fail completely.
Within a processing chamber, processing conditions vary. The variations in processing conditions such as temperature, gas flow rate and/or gas composition greatly affect the formation and, thus, the performance of the integrated circuit. Sensors may be placed at various points in and about a processing chamber in order to attempt to measure processing conditions experienced by a workpiece. However, even where sensors are placed close to a workpiece, conditions experienced by a sensor may be different from conditions experienced by a workpiece, especially in a rapidly changing environment such as during a rapid temperature change.
Using sensors attached to a sensor substrate of the same or similar material and dimensions to those of a production substrate provides an accurate measure of process conditions because measurements are made at locations within, or on a surface of, a sensor substrate. The material properties of the sensor substrate are close to the material properties of production substrates. A sensor substrate with sensors and related electronic circuits may be considered a Process Condition Measuring Device (PCMD). PCMDs may be subject to the same processing as production substrates so that the processing conditions experienced by production substrates may be accurately estimated. In some examples, data are relayed to a unit outside a processing system in real time, either by a wired connection or wirelessly. Alternatively, process condition data may be stored in a memory in the PCMD and later recovered for analysis.
Gradients and variations exist throughout the chamber for virtually all process conditions. These gradients, therefore, also exist across the surface of a substrate. It is generally desirable to obtain more than one measurement for a particular processing condition. By gathering measurements of a processing condition at various points across a substrate, the gradient of that processing condition across a production substrate may be estimated. However, such measurements may be affected by differences between production substrates and PCMDs. Several designs have been described for process condition measuring devices that resemble production substrates in their physical properties or dimensions.
In some applications, PCMDs may be exposed to harsh conditions that may damage certain components, or cause disturbance in measurements. Radio Frequency (RF) or other electromagnetic radiation in some environments may affect electronic components in a PCMD, for example, by causing noise that disturbs readings. RF radiation is used in various processes in the semiconductor industry (and other industries). For example, etching of semiconductor substrates may use an RF plasma that could cause damage to electronic components.
Therefore, there is a need for a PCMD that has shielding that allows the PCMD to operate in an environment having high-energy electromagnetic radiation. There is also a need for such a PCMD to operate in an environment where etching of material from the PCMD may occur, without the etched material contaminating the processing system.